This application is a national stage of International Application No. PCT/EP2007/000455, filed Jan. 19, 2007, the entire disclosure of which is herein expressly incorporated by reference.
The invention relates to a fluid flow machine, especially of the type which can be used with internal combustion engines with pumps operated by exhaust gas and with the fuel supply of fuel cells with a compressor.
U.S. Pat. No. 5,087,176 discloses a turbo compressor with a compressor wheel and a turbine wheel on a hollow shaft. Air circulates through the interior of the shaft to protect the shaft bearing from overheating, and the shaft is insulated thermally against the turbine wheel. The cooling air, which is drawn in from the pressure side of the compressor, must itself be cooled with high pressures, before it can be used to cool the bearings.
With a gas supply unit for a fuel cell system according to Published U.S. patent application Ser. No. 2005/0066680 A1, a control unit and a drive unit are formed with channels, through which a cooling medium flows. A part of the channels is assigned to the mounting of a rotor of the drive unit. The combustion gas supply for the fuel cell system takes place in such a manner that the combustion gas has an additional cooling effect on the rotor bearing. The combustion gas is conducted along the bearing by the suction effect of an impeller of a turbo compressor.
One object of the present invention is to provide a fluid flow machine which improved efficiency and an improved cooling effect on the bearings, with little complexity.
This and other objects and advantages are achieved by the fluid flow machine according to the invention, in which the shaft of an impeller is held in radial bearings and in an axial bearing. The axial bearing comprises a revolving part which acts as a cooling fluid transport device. The cooling fluid is transported from the intake side of the impeller to bearing parts of the shaft, and to further components to be cooled. The bearings can be formed as roller bearings, sleeve bearings or gas bearings.
The revolving part may comprise a disk which is seated on the shaft in a torque-proof manner. It can be equipped for transporting the cooling fluid with blades, or it can have helical channels. The disk can especially have hollow chambers in which channels guide the fluid in the direction of a bearing surface. The channels or radial bores are preferably flown through in a radial manner.
The shaft is formed hollow in an advantageous embodiment, and the cooling fluid flows through the interior of the shaft.
The part of the axial bearing formed as a cooling fluid transportation device does not compress the cooling fluid to such an extent as the working fluid on the pressure side of the impeller. The cooling fluid is taken in on the intake side of the impeller, where the pressure and temperature are in regions which allow an improvement of the efficiency, as no working fluid is branched off from the pressure side. The part of the working fluid taken in as cooling fluid has a lower temperature than the working fluid on the pressure side, so that the bearings over which the cooling fluid flows can be cooled efficiently.
In a particularly advantageous arrangement of the invention, the impeller is driven by an electric machine. Moreover, it is also particularly advantageous if the electric machine, which typically operates as an engine, is cooled by the transported cooling fluid. The above-mentioned advantages then result with regard to the transportation and the pressure level also for the cooling fluid used for cooling the engine. The engine cooling can also be realized without additional cooling medium transportation.
If the fluid flow machine is driven by a turbine impeller, or the drive is supported at least by means of a turbine impeller, it is possible to transport cooling fluid by means of blades on the rear side of the turbine impeller, either alternatively or in addition to the cooling medium transportation part. In this case, the cooling fluid transported from the intake side of the compressor impeller can be supplied to the expansion process of the turbine.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.